1. Field of the Invention
This invention pertains to a new class of optical devices based on resonant leaky modes in periodically modulated structures. It is based on dielectric and semiconductor structures that are relatively thick, which can support a large number of quasi-guided or leaky, resonant modes. Embodiments disclosed herein include filters with comb-like spectral characteristics with a large number of spectral resonance peaks that may be useful in applications such as telecommunications.
2. Description of the Related Art
There is increasing worldwide interest in guided-mode resonance (GMR) effects that originate in quasi-guided, or leaky, waveguide modes induced on patterned films with subwavelength periods. Nanopatterned resonant elements yield versatile spectra with a rich variety of possible surface-localized photonic states. It has been shown that a single periodic resonance layer with one-dimensional (1D) periodicity enables narrow-line bandpass and bandstop filters, polarizers, reflectors, and polarization-independent elements. Numerous applications including laser mirrors, ultrasensitive biosensors, absorption enhancement in solar cells, security devices, tunable filters, nanoelectromechanical display pixels, leaky-mode nanoplasmonics, and others have been suggested. In this application, we present resonant mode multiline comb-like filters and numerical results indicating the effectiveness and potential use of such filters.
Much past research on GMR devices has focused on thin periodic layers supporting only a single leaky mode and associated resonance within a specified spectral band. In contrast, Liu and Magnusson explored properties of multiorder multimode GMR elements to design wideband and multiwavelength filters. Subsequently, Boonruang et al. designed multiline GMR filters using two-dimensional (2D) grating structures with rectangular and hexagonal grids. They implemented spectral location control by inducing leaky modes into specific directions on these grids. Greenwell et al. designed 1D multiwavelength GMR filters based on multimode waveguides with particular emphasis on resonance separation control.